Marc,
We've 170k Kms on our e53.
Heres what we've had to do and is what I'd look for in a replacement
Replaced all the shocks
Changed gearbox oil
Regular servicing (more than the prescribed amount)
Replaced steering wheel trim (the original will be worn by now)
Replace cv boots
Fit hid bulbs
I'd want decent tyres on the car too, preferably original spec tyres
And some tax

I think that's about it...